''Phorusrhacos'' ( ) is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of giant

flightless Flightless birds are birds that through evolution lost the ability to fly. There are over 60 extant species, including the well known ratites (ostriches, emu, cassowaries, rheas, and kiwi) and penguins. The smallest flightless bird is the ...

terror birds Phorusrhacids, colloquially known as terror birds, are an extinct clade of large carnivorous flightless birds that were one of the largest species of apex predators in South America during the Cenozoic era; their conventionally accepted temporal ...

that inhabited

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...

during the

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

epoch. ''Phorusrhacos'' was one of the dominant land predators in South America at the time it existed. It is thought to have lived in

woodland A woodland () is, in the broad sense, land covered with trees, or in a narrow sense, synonymous with wood (or in the U.S., the ''plurale tantum'' woods), a low-density forest forming open habitats with plenty of sunlight and limited shade (see ...

s and

grasslands A grassland is an area where the vegetation is dominated by grasses (Poaceae). However, sedge (Cyperaceae) and rush (Juncaceae) can also be found along with variable proportions of legumes, like clover, and other herbs. Grasslands occur natural ...

Discovery and naming

Remains are known from several localities in the

Santa Cruz Formation The Santa Cruz Formation is a geological formation in the Magallanes/Austral Basin in southern Patagonia in Argentina and in adjacent areas of Chile. It dates to the late Early Miocene epoch, and is contemporaneous with eponymous Santacrucian ...

and

Monte León Formation Monte may refer to: Places Argentina * Argentine Monte, an ecoregion * Monte Desert * Monte Partido, a ''partido'' in Buenos Aires Province Italy * Monte Bregagno * Monte Cassino * Montecorvino (disambiguation) * Montefalcione Portugal * Monte ...

in the Santa Cruz Province, of Argentina. Among the bones found in the strata of the Santa Cruz Formations (now considered as mainly of mid-

date) was the piece of a mandible which

Florentino Ameghino Florentino Ameghino (born Giovanni Battista Fiorino Giuseppe Ameghino September 19, 1853 – August 6, 1911) was an Argentine naturalist, paleontologist, anthropologist and zoologist, whose fossil discoveries on the Argentine Pampas, especially ...

discovered in early 1887 and the same year at first described as that of an

edentate Xenarthra (; from Ancient Greek ξένος, xénos, "foreign, alien" + ἄρθρον, árthron, "joint") is a major clade of placental mammals native to the Americas. There are 31 living species: the anteaters, tree sloths, and armadillos. Ex ...

mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...

which he named ''Phorusrhacos longissimus''. The generic name is derived from Greek -φόρος, (-''phoros''), an element meaning "bearer" in word combinations, and ῥάκος, (''rhakos''), "rag" or "wrinkle", probably in reference to the wrinkled jaw surface. When the original derivation was no longer understood, other translations were given, such as the literal translation of "Rag-Thief", and "branch-holder" from the mistaken assumption the name had been intended to be derived from a Greek ''rhakis'', "branch". The specific name means "very long" in

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

, again in reference to the lower jaws. The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

is the mandible, specimen MLP-118 (Museo de La Plata). In 1889 Ameghino emended the name to a more grammatically correct ''Phororhacos'' but the earlier name has priority. In 1891, it was by him recognized to be a bird.

Description

''Phorusrhacos'' had a skull nearly long, stood nearly tall, and probably weighed nearly , as much as a male

ostrich Ostriches are large flightless birds of the genus ''Struthio'' in the order Struthioniformes, part of the infra-class Palaeognathae, a diverse group of flightless birds also known as ratites that includes the emus, rheas, and kiwis. There are ...

. It had very strong legs, capable of running at high speed, stubby, flightless wings, a long neck, and a proportionately large head. This ended in a huge, hooked beak that could tear through flesh easily, or stab into prey. The lower jaw was smaller than the upper jaw. There were three toes on each of the feet, all of which were armed with sharp claws.

Classification

''Phorusrhacos'' was part of the group called the

Phorusrhacidae Phorusrhacids, colloquially known as terror birds, are an extinct clade of large carnivorous flightless birds that were one of the largest species of apex predators in South America during the Cenozoic era; their conventionally accepted temporal ...

, which is an extinct group of flightless, cursorial carnivorous birds that occupied one of the dominant, large land-predator niches in South America from the lower

Eocene The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...

to the

Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...

. They dispersed into North America during the

Great American Biotic Interchange The Great American Biotic Interchange (commonly abbreviated as GABI), also known as the Great American Interchange and the Great American Faunal Interchange, was an important late Cenozoic paleozoogeographic biotic interchange event in which lan ...

(∼3 Ma). Some remains from Africa and Europe and the

Paleocene The Paleocene, ( ) or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), E ...

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

have been referred to this clade or identified as phylogenetically related to the extant South American

seriema The seriemas are the sole living members of the small bird family Cariamidae, which is also the only surviving lineage of the order Cariamiformes. Once believed to be related to cranes, they have been placed near the falcons, parrots and passerin ...

s, but these assignments remain controversial. The following cladogram follows the analysis of Degrange and colleagues, 2015:

References

{{Taxonbar, from=Q131317 Phorusrhacinae Bird genera Extinct flightless birds Serravallian extinctions Burdigalian first appearances Miocene birds of South America Laventan Colloncuran Friasian Santacrucian Colhuehuapian Neogene Argentina Fossils of Argentina Fossil taxa described in 1887 Taxa named by Florentino Ameghino